8 
PROFESSOK TYNDALL ON THE ABSORPTION AND 
duced a deflection of about 
r. 
Hydrogen from zinc and sulphuric acid produced a deflection of about 
1 °. 
Hydrogen obtained from the electrolysis of water produced a deflection of about 
1 °. 
Oxygen obtained from the electrolysis of water, and sent through a series of eight 
bulbs containing a strong solution of iodide of potassium, produced a deflection of about 
1 °. 
In the last experiment the electrolytic oxygen was freed from its ozone. The iodide 
of potassium was afterwards suppressed, and the oxygen, plus its ozone, admitted into 
the tube ; the deflection produced was 
4° 
Hence the small quantity of ozone which accompanied the oxygen in this case trebled 
the absorption of the oxygen itself^. 
I have repeated this experiment many times, employing different sources of heat. 
With sources of high temperature the difference between the ozone and the ordinary 
oxygen comes out very strikingly. By careful decomposition a much larger amoimt of 
ozone might be obtained, and a corresponding large effect on radiant heat produced. 
In obtaining the electrolytic oxygen I made use of two different vessels. To diminish 
the resistance of the acidulated water to the passage of the current, I placed in one vessel 
a pair of very large platinum plates, between which the current from a battery of ten of 
Geove’s cells was transmitted. The oxygen bubbles liberated on so large a surface were 
extremely minute, and the gas thus generated, on being sent through iodide of potas- 
sium, scarcely coloured the liquid ; the characteristic odour of ozone was also almost 
entirely absent. In the second vessel smaller plates were used. The bubbles of oxygen 
were much larger, and did not come into such intimate contact with either the platinum 
or the water. The oxygen thus obtained showed the characteristic reactions of ozone, 
and with it the above result was obtained. 
The total amount of heat transmitted through the tube in these experiments pro- 
duced a deflection of 
71°-5. 
Taking as unit of heat the quantity necessary to cause the needle to move from 0° to 
1°, the number of units expressed by the above deflection is 
308. 
Hence the absorption by the above gases amounted to about 0'33 per cent. 
I am unable at the present moment to range with certainty oxygen, hydrogen, nitro- 
gen, and atmospheric air in the order of their absorptive powers, though I have made 
several hundred experiments with the view of doing so. Their proper action is so small 
that the slightest foreign impurity gives one a predominance over the other. In 
* It will be seen further on that this result is in harmony with the supposition that ozone, obtained in 
the manner described, is a compound body. 
